Cracking hydrocarbons in presence of trimethylene chlorobromide



Patented June 15, 1948 CRACKING HYDROCARBONS IN PRESENCE OF TRIMETHYLENE CHLOROBROMIDE Hillis O. Folkina, Skokie, 111., assignor to The Pure Oil Company, Chicago, 11]., a corporation of Ohio No Drawing. Application June 20, 1945,

Serial No. 600,840

1 10 Claims.

This invention relates to the conversion of hydrocarbons, and particularlyto the conversion of higher boiling hydrocarbons into lower boiling ln'drocarbons, and t the conversion of hydrocarbons into less saturated hydrocarbons.

One of the objects of the invention is to provide a method for converting hydrocarbons into lower boiling hydrocarbons.

Another object of the invention is to convert hydrocarbons int less saturated hydrocarbons.

Still another fibject of theinvention is to accelerate the rate of cracking in thermal cracking operations.

A further object of the invention is to provide a sensitizer for assisting in the thermal cracking of hydrocarbons.

Other objects of the invention will become ap parent from the following description,

In accordance with my invention hydrocarbons to be converted are subjected to conversion con ditions of time, temperature and pressure in ad-v mixture 'with a small amount of trimethylene chlorobromide (ClCHaCHaCHzBI'). The trimethylene chlorobromide is admixed with the hydrocarbons undergoing reaction in amounts equivalent to approximately 0.001 to 3% by weight of bromine, based on the weight of the hydrocarbon undergoing cracking. Where cracking of liquid hydrocarbons to gasoline-boiling hydrocarbons foguse in motor fuel is practiced, I prefer to use trimethylene chlorobromide in amountsequivalent to less than 0.1% by weight of bromine,

, siilicellarger amounts have a deleterious effect on the lead susceptibility of the resulting gasoline- Although higher amounts of trimethylene chlorobromide than those above specified may be used to, sensitize the cracking reaction, within the range above specified the increase in reaction rate is'very' marked and formation of large amounts of undesirable bromine and chlorine in the reaction productsis avoided- Y The trimethylene chlorobromide may be mixed with the hydrocarbon oil vapor or with gas such as propane and butane undergoing conversion, prior to charging it to the reaction zone, or the sensitizer may be separately injected directly into 1 .';the reaction zone. The sensitizer may be mixed with the oil in liquid state, or where it is in- Jected into the reaction zone it may be injected either in the form of liquid or vapor. Care should be taken not to heat the sensitizer to such a temperature that decomposition thereof occurs .until it is contacted with the hydrocarbons to be converted at reaction temperature.

Cracking of hydrocarbons in the presence of as trimethylene chlorobromide may be carried out under subatmospheric, atmospheric or .superatmosphericpressure, and at temperatures ranging from the lowest temperature at which cracking will occur to temperatures of approximately 2000" F. depending on the nature of the charging stock and the type of product it is desired to produce. Where cracking of hydrocarbon oil is conducted for the purpose of making lower boiling liquid hydrocarbons, such as gasoline, temperatures ranging from approximately 650 to 1200 F. may be used. Where it is desired to crack hydrocarbon oils or gases to aromatic hydrocarbons, temperatures of approximately'1000" to 1500 F. may be used. Where a conversion is carried out for the purpose of converting hydrocarbon oils to butadiene, conversion temperatures will. be in the vicinity of 1300 to 1600 F.; and where hydrocarbon oils are cracked to gaseous hydrocarbon, temperatures of approximately l500 to 2000". 1-". may be used.

In order to demonstrate the efficacy of trimethylene chlorobromide as a cracking sensitizer, a series of runs were made using n-butane as charging stock. The runs were made in laboratory apparatus constructed of Pyrex glass and at a temperature of 977 F. Before each run the reaction vessel was evacuated to approximately 0.001 mm. or less of mercury, while the vessel was maintained at the aforesaid reaction temperature. Butane' was then charged to the reaction chamber admixed with the desired quantity of sensitizer until the pressure in the reaction chamber was approximately atmospheric. Pressure increases in the reaction chamber were noted at different intervals ranging from .5 to 2 minutes until a pressure increase of 25% had been attained. When the pressure increased 25% the reaction chamber was quickly evacuated and the reaction products were analyzed for acidic-constituents by absorption in caustic potash solution; for unsaturatesby absorption in fuming sulfuric acid; for hydrogen by contraction in' volume due to water formation; and for carbon monoxide by oxidation followed by absorption in caustic potash solution.

A series of blank runs were also made in order to compare the rate of reaction in the presence of trimethylene chlorobromide with the rate of reaction in the absence of sensitizers. The results obtained in the several runs are set forth in the following table. The blank run represents the average of four blank runs. In addition to the blank runs and the two trimethylene chlorobromide runs, data for runs sensitized with sensitized runs for n-propyl chloride and n-propyl bromide are also set forth in the table in order to show the marked superiority of trimethylene chlorobromide over each of these sensitizers.

In another run in which the charge rate was 170 grams per hour and in which no sensitizer was used, 10.2% by weight of the gas oil was converted to liquid hydrocarbons boiling below Table Time in Minutes for Sensitization 11...... Products, Moi M I t AP 01- for AP 01- per cent 8!"- Bensitizer @5555: n. Residue 11% ram. 25% 11% 12.0% 25% Acids m Trimethylena chlorobromide o. s o. m 0.13 1. w a a 10. s 10.8 o. o 20. e 0.1 0.1 1s. 2 Do 0.25 0.44 1.118 4.20 so u 5.1 0.1 24.6 0.4 1.3 13.1 2-21 7-92 21-55 0.2 24.3 0.2 1.4 74.0 1. 0 1. so 4.110 12. 2s 1. e 1. e 1. a 0.1 22. e o. 2 o. 3 1a a 0.5 1.65 5.47 14.98 1.3 1.3 1.3 0.0 22.9 0.0 0.0 77.1 0.25 1.04 5.73 16.22 1.3 1.3 1.2 0.0 22.5 0.0 0.0 77. 5 1.0 0. a1 .0. a; 2. es 1. 7 8.0 1. a 0.0 21.2 o. o o. o 70. s 0.5 0.6 1.63 4.03 3.7 4.0 4.0 0.0 24.4 0.3 0.3 75.0 0. 25 1. 94 5. 3. 5 3. 8 3. 9 0. 1 23. 0 0. 0 0. 0 76. 9

Sensitization factors for pressure increases of 5%, 12.5% and are obtained by dividing the time required for these same pressure increases in the blank run by the time required in the the same pressure increases. Sensitization factor is therefore a direct indication of acceleration in the rate of reaction caused by the sensitizer.

By reference to the table it will be seen that 0.5 mol per cent of trimethylene chlorobromide was not only more effective than 0.5% of either n-propyl chloride or n-propyl bromide, but was more effective than 1% of either of the latter two compounds. Thus, while n-propyl chloride sensitizes the reaction to a small extent, and n-propyl bromide sensitizes the reaction to a much greater extent than n-propyl chloride, trimethylene chlorobromide is far superior to either.

As appears from the table, n-propyl bromide increases in effectiveness as the amount of n-propyl bromide increases. If the bromine content of the molecule is a measure of its sensitizing eflectiveness, then since one mol percent of n-propyl bromide contains the same amount of bromine as does one mol per cent of trimethylene chlorobromide, the normal expectancy would be that one mol per cent of n-propyl bromide would be more eifective than 0.5 mol per cent of trimethylene chlorobromide, particularly in view of the poor sensitizing efiect of n-propyl chloride. It has been found however that the same acceleration in reaction can be obtained by a much smaller amount of trimethylene chlorobromide than of n-propyl bromide.

In order to further demonstrate the eflicacy of trimethylene chlorobromide in sensitizing crackingreactions, a series of runs were made in a small laboratory stainless steel continuous cracking apparatus using Pennsylvania gas oil as charging stock at a temperature of 977 F. and at atmospheric pressure. In one run gas oil was mixed with- 0.5% by weight of trimethylene chlorobromide. The gas oil was charged through the cracking unit at a rate of 164.8 grams per hour. In a one pass cracking operation 17% by weight of the charge was converted to liquid hydrocarbon boiling below 400 F., and 8.9% by weight of the charge was converted to gaseous hydrocarbons.

In another run in which the charge rate was 166 grams per hour and in which trimethylene chlorobromide was present in the amount of 0.25% by weight of the 011, 13.7% by weight of the. charge was converted to liquid hydrocarbons boiling below 400 F. and 8.5% by weight of the chargewas converted to gas.

400 F., and 5.9% by weight of the gas oil was converted to gas.

From the foregoing three runs it will be seen that the cracking rate in the presence of trimethylene chlorobromide is greatly increased over that in the absence of sensitizer.

It is apparent from the analysis of reaction products that the reaction products obtained. using trimethylene chlorobromide as sensitizer are very little different than those obtained without any sensitizer. It is also apparent from the large amount of unsaturates obtained and the very small amount of hydrogen obtained that the reaction is primarily one of cracking of the molecule at the carbon to carbon bond.v

The invention is useful in connection with the present type of purely thermal cracking operations, either of the low or high pressure type, without the necessity of changing either the operation of such process or the apparatus required, except to make provision for charging a small amount of trimethylene chlorobromide to the operation. The invention is also useful in conjunction with known types of catalytic cracking operations, including the so-called moving bed catalytic cracking, Fixed bed catalytic cracking and Fluid catalytic cracking processes.

It is claimed:

1. The method of cracking hydrocarbons comprising subjecting said hydrocarbons. to suitable cracking conditions of time, temperature and pressure in the'presence of a small amount of trimethylene chlorobromide.

2. Method in accordance with claim 1 in which the amount of trimethylene chlorobromide is equivalent to between 0.001 and 3% by weight of bromine based on the hydrocarbons undergoing cracking.

3. Method in accordance with claim 1 in which the hydrocarbons are chiefly butanes and the temperature is between 1000 and 1500 F.

4. Method in accordance with claim 1 in which the hydrocarbons are chiefly propane.

' 5. The method of cracking butane comprising subjecting butane to temperatures of the order of 977 F. in the presence of trimethylene chlorobromide equivalent to 0.001 to 3% by weight of bromine based on the butane.

6. The method of cracking hydrocarbon liquids to gasoline boiling hydrocarbons comprising heating said liquids to a temperature of approximately 650 to 1200" F. in the presence of a small amount of trimethylene chlorobromide.

7. Method in accordance with claim 6 in which the amount of trimethylene chlorobromide is equivalent to between 0.001 and 3% by weight of REFERENCES CITED oromine based on the hydrocarbon liquid. 1

8. Method in accordance with claim 6 in which y? fig gg g g are of record in the the amount of trimethylene chlorobromide is equivalent to between 0.001 and 0.1% by weight of 5 UNITED STATES PATENTS bromine based on the hydrocarbon liquid,

9. Method in accordance with claim 1 in which ggi g fi i the cracking reaction is carried out in the absence 2213345 Marschner Sept 1940 of other catalysts.

10. Method in accordance with claim 6 in which 10 OTHER REFERENCES the cracking reaction is carried out in the absence Troncv t 1 Chem, Abstracts, vol. 25, 3957-8 of other catalysts. 31

HILLIS O. FOLICINS. 

